Manufacture of magnesium



c.r BAssEREAu MANUFACTURE oF MAGNESIUM lFiled Sept. 12, 1945l `Iran. 22,1952 Patented Jan. 22, 1952 MANUFACTUBE F MAGNESIUM Georges Bussereau,Paris, France, signor to Societe Electro-Metallurgique du Planet, Paris,

France Application September 12. 1945, Seria-l No. 815,841 In FranceJune 12, 1942 Section 1, Public Law 690, August 8, 1946 Patent expiresJune 12, 1962 13 claimt. (ci. zes-19) My invention relates to theproduction of magnesium by thermal reduction of an ore of that metal.such` as dolomite. Dolomite mixed with a charge of a reducer such asferro-silicon, is submitted to electrical heating. Such reaction isaccomplished within a furnace under vacuum, to avoid the combustion ofthe magnesium when and as it appears or its transformation .into oxides,nitrides and other compounds. Thev magnesium vapors are condensed in anenclosure connected to the furnace.

To obtain the best yield for the reduction of the ore, it is customaryto maintain in the furnace a high degree of vacuum. under which themagnesium vapors will condense to the solid state. In that case, thereduction operation must be followed by a fusion of the condensedmagnesium in order to obtain a compact ingot or mass.

When it is desired to obtain magnesium in the liquid state directly,that is to say to condense to the liquid state the vapors issuing fromthe reduction enclosure, the condenser and consequently the reductionfurnace must be under a pressure somewhat higher than for the usualcondensation to the solid state. But in such a case, there is a risk ofan insufficient yield for the reduction operation and also of magnesiumvapors being driven along into the vacuum pump piping where they may,when condensing; cause prejudicial clogging.

My invention has for its object to provide an efficient method forobtaining magnesium directly in the liquid state while obviating theabove mentioned drawbacks.K

The method according to my invention consists in providing in thecondenser two successive communicating zones, the rst zone communicatingwith the reduction enclosure and the second zone with the vacuum pump,in establishing in said zones temperature and pressure conditionsdifferent from one zone to the other and adapted for the first zone toassure the condensation of magnesium vapors to the liquid state and forthe second zone the condensation to the solid state, the communicationbetween the two zones being arranged to create (for instance by means ofa throttle) in the gaseous current sucked by the pump a loss of pressurecapable of maintaining in the rst zone an excess of pressure withrespect to the second zone.

Under those conditions, the vacuum pump is in direct communication onlywith the zone of the condenser where a comparatively low temperatureprevails, corresponding to a very low 2 vapor tension of the magnesium.such zone consequently condensing and practically retaining all of themagnesium and avoiding the passage of vapors of that metal into thevacuum pump.

As to the reduction of the ore, though it takes place under pressureconditions enabling a condensation to the liquid state, it isnevertheless accomplished with a satisfactory yield as such pressure isvery little above the minimum required for obtaining the condensation tothe liquid state. Such minimum value is comparatively low; and thepressure in the reduction furnace differs from the high degree vacuumprevailing in the zone of condensation to the solid state only by thesmall value corresponding to the loss of pressure produced in the vaporscurrent between the rst and the second zones in the condenser. It isthus possible to maintain the pressure in the reduction furnace at avalue low enough to have a good yield, while such pressure is suilicientto ensure the condensation to the liquid state in the first zone of thecondenser.

The method according to my invention may be carried out by maintainingthe rst zone of the condenser at a temperature of the order of 660 C.and at a pressure of the order of 2 millimeters of mercury, while thesecond zone is maintained at a temperature slightly lower than 400 C.and at a very low pressure equal to the tension of the magnesium vaporsat that temperature.

A particularly advantageous embodiment of my invention consists inproviding small dimensions for the condenser in the rst zone ofcondensation to the liquid state, and in continuously eliminating thecondensed liquid magnesium when and as it is formed. To that end, thecompartment of the condenser where the magnesium vapors condense to theliquid state communicates at its lower part with a' uid tight chambercontaining an ingot mould into which the liquid metal falls.

At its upper part the rst zone for the liquid condensation communicateswith the second zone for the solid condensation through an aperture of-small section which is consequently able to cause, on the path of thegases passing from the first to the second zone, a loss of pressureequal to the difference of pressure which it is desirable to establishfrom one zone to the other.

In the zone for the liquid condensation the pressure and temperaturemust correspond to the indications of the phase diagram for the liquidphase. i. e. a temperature and pressure slightly higher than the triplepoint.

The temperature. controlled by a pyrometer, is maintained at the desiredvalue by any suitable means.

Under those conditions. the vapor streamlets reaching the partitionseparating the iirst zone of liquid condensation from the second zone ofsolid condensation are condensed when and as they arrive and the liquidfalls into the ingot mould placed in the fluid-tight chamber which isunder the same pressure or vacuum conditions as the first zone withwhich it communicates.

The metal may settle in the ingot mould which is either at ordinarytemperature or hot.

In case it settles in an ingot mould at ordinary temperature, only thedischarging pipe supplying the liquid to the ingot mould is maintainedat the temperature of the condenser zone of liquid condensation, thechamber where the ingot mould stands being left at the ordinarytemperature. The ingot mould contains a certain quantity of oil and isalso surrounded by an oil bath so that the liquid drops settle in theoil of the ingot mould, in the form of small balls separated from theirimpurities.

The oil surrounded the ingot mould is provided for the sake ofprecaution, in case some streamlets of metal vapors would exceptionallypass through the discharging orice and penetrate into the chamber of theingot mould. They will then condense in the oil which is the coldestpoint of the chamber containing the :ingotmould.

If the metal settles in a hot ingot mould, said ingot mould is laid on abase made of insulating material under which is provided a fluid-tightcooled door. All the upper part and the insulating bottom of the ingotmould chamber are carefully heat insulated or even reheated ifnecessary, so that the ingot mould will be at the same temperature asthe condenser zone of liquid condensation. In that case the liquidilowing into the ingot mould is maintained liquid.

Before taking the ingot mould out of the chamber, the heat-insulatingmaterial or the heating means surrounding the ingot mould chamber istaken oi and replaced by waterjackets which in a few minutes produce thesolidification of the metal in the ingot mould. It is then suillcient toopen the door at the lower end of the chamber to take off the ingotmould and the solidiiied metal which it contains.

The oil is filtered, if necessary, before being used again.

The accompanying drawings show merely as an example an embodiment of acondenser improved according to my invention.

Fig. l is a vertical view, with an axial section of the completecondenser.

Fig. 2 is a cross section along line II-II of Fig. l.

Fig. 3 is an axial section of a modified design of the ingot-mouldchamber.

Fig. 4 is a front view, partly broken away, of the door to thecondensing chamber, showing the yoke swung aside.

The furnace in which the reduction of the charge takes place (byelectrical heating under vacuum) may be of any suitable type and forthat reason it is neither shown on the drawings nor described.

The reaction enclosure i of that furnace is communicating at one of itsends with the condenser comprising for instance, an iron sheet envelope2 shaped as a truncated cone, having the same horizontal axis as theduct 3 of refractory material connecting the condenser with the reactionenclosure.

. According to the invention, in the part of the condenser adjacent tothe furnace there is provided a chamber 4, called liquefaction chamber.constituted by refractory walls 5, 5a and 6, and directly communicatingwith the reaction enclosure of the furnace through the duct 3. At itsend opposite to duct 3, the chamber 1I comprises a refractory wall 6tightly set on thel lateral walls 5 and 5a and through which there isprovided a duct 1 of very small section, connecting the chamber l withthe extremity of the condenser which constitutes the crystallizationchamber 8. The wall 6 plays the part of a door giving access to theliquefaction chamber; it is provided with a handle 9 or any othergrasping means, and it is maintained in its place by a sheet-iron casingI0 constituting the inner wall of the crystallization chamber. Suchcasing I0 comprises an end-plate II. carefully heatinsulated, which atthe center bears a fastening clamp I2 placed at the end of a screw I3that is engaged with the screw threads of a fork-link, the ends I4 ofwhich bear on the wall 2 of the condenser.

The screw I3, fork link, and door I1 are not claimed herein, and thereis not represented the reheating or cooling means which may permissiblybe used for maintaining the temperature at about 400 C. inside thecrystallization chamber 8. 'Such chamber communicates. through the smallvhole I5 provided in the end-plate II, with the back capacity I6 closedby a fluid-tight door I1, and communicates also with the vacuum sourcethrough the duct I8.

The liquefaction chamber 4, the cross section of which is circular asshown on Figure 2, comprises at its lower part an aperture I9 above afunnel-shaped cavity 20 provided in a refractory block 2l set in asheet-iron casing 22 welded with the wall 2 of the condenser, outwardlyinsulated at 23 along the height of block r2l and permissibly lprovidedwith reheating means. The chamber containing the ingot mould is placedunder the casing 22 to which it is tightly connected by flanges 24. Itis surrounded by a jacket 25 in which cooling water is circulated. Theingot mould 26 is immersed in an oil bath, as above explained.

Such arrangement is suitable for the case where the metal formed in theliquid state in the liquefaction chamber 4 is gathered in solid form inthe ingot-mould 26. The jacket 25 enables to maintain in the ingot mouldchamber a temperature which is suilciently low so that the liquid metalflowing through the pipe 30 will solidify when reaching the ingot mould26. The latter may advantageously contain oil into which the liquiddrops fall and solidify in the shape of small balls after having beenseparated from their impurities.

When it is desired that the formed liquid metal should fall into theingot mould and be maintained there in the liquid phase during all theoperation, it is possible to use the arrangement shown on Figure 3 wherethe ingot mould is immediately adjacent to the block 2I and is laid forinstance on a base constituted by a refractory and insulating mass 21.The ingot mould chamy as water is circulating. The liquid metal of theingot mould is solidified and the operation is ended by breaking thevacuum in the furnace and taking oil. -the ingot mould. At the sametime, the casing I0 is taken away and it is rapidly introduced into acooled, tightly closed enclosure of suitable shape, where the vacuum isestablished so that the gathered crystals may cool without beingsubjected to the action of air so as to avoid any loss of metal.

01' course the invention which was described principally in respect ofits application to the case of magnesium is applicable to theproduction, in similar conditions, of metals which are obtained bycondensation of their vapors.

What is claimed is:

1. Apparatus for the production of a metal by condensation of its vaporswhich comprises a reaction chamber for the heat treatment of the oreunder vacuum, a condenser comprising two successive zones communicatingone with the other, the first zone communicating with the reactionchamber and the second zone with a vacuum pump, means to establish andmaintain in said zones respectively temperature and pressure conditionsadapted to cause the metal vapors to condense in the first zone to theliquid state and in the second zone to the solid state, a throttle beingprovided in the communication between the two zones to create in thevapors current sucked by the vacuum pump a loss of pressure capable ofensuring the required difference oi pressure between the first zone andthe second zone.

2. Apparatus for the production of a metal by condensation of its vaporswhich comprises a reaction chamber for the heat treatment of the oreunder vacuum, a condenser comprising two successive zones communicatingone with the other, the first zone communicating with the reactionchamber and the second zone with a vacuum pump, means to establish andmaintain in said zones respectively temperature and pressure conditionsadapted to cause the metal vapors to condense in the first zone to theliquid state and in the second zone to the solid state, the said firstzone being separated from the second zone by a partition provided at itsupper part with an orice to create in the vapors current sucked by thevacuum pump a loss of pressure capable of ensuring the requireddiiference of pressure between the first zone and the second zone.

3. Apparatus for the production of a metal by condensation of vitsvapors winch comprises a reaction chamber for the heat treatment of theore under vacuum, a condenser comprising two successive zonescommunicating one with the other, the ilrst zone communicating with thereaction chamber and the second zone with a vacuum pump, means toestablish and maintain in said zones respectively temperature andpressure conditions adapted to cause the metal vapors qll vtocondenseintheiirstsonetotheliquidstate and in the second zone to thesolid state, the communication between the two sones being arranged tocreate in the vapors current sucked by the vacuum pump s. loss ot`pressure capable or ensuring the required diiiernce of pressure lbetweenthe iirst zone and the second zone. a tight chamber in which is placedan ingot mould to receive the metal, said chamber communieating with thelower part oi the first zone of the condenser in which the metalvaporscondense to the liquid state.

4. Apparatus for the production of a metal by condensation of its vaporswhich comprises a reaction chamber for the heat treatment of the oreunder vacuum. a condenser comprising two successive zones communicatingone with the other, the first zone communicating with the reactionchamber and the second zone with a vacuum pump, means to establish and'maintain in said zones respectively temperature and pressure conditionsadapted to cause the metal vapors to condense in the first zone to theliquid state and in the second zone to the solid state, thecommunication between the two zones being arranged to create in thevapors current sucked by the vacuum pump a loss of pressure capable oi'ensuring the required diiierence of pressure between the ilrst zone andthe second zone, a tight chamber in which is placed an ingot mould toreceive the metal, said chamber communicating by an orifice through itsupper part with the lower partvot the iirst zone ot the condenser inwhich the metal vapors condense to the liquid state, and means tomaintain the upper part of said chamber provided with said orificethrough which the metal is discharged to the ingot mould at the sametemperature as the iirst zone of the condenser.

5. Apparatus for the production of a metal by condensation of its vaporswhich comprises a reaction chamber for the heat treatment of the oreunder vacuum, a condenser comprising two successive zones communicatingone with the other,

' the first zone communicating with the reaction chamber and the secondzone' `with a vacuum pump, means to establish and lmaintain in saidzones respectively temperature and pressure conditions adapted to causethe metal vapors to condense in the rst zone to the liquid state and inthe second zone to the solid state, the communication between the twozones being arranged to create in the vapors current sucked by thevacuum pump a loss of pressure capable of ensuring the requireddiiierence of pressure between the iirst zone and the second zone, atight chamber in which is placed an ingot mould to re celve the metal,said chamber communicating by an oriiice through its upper part with thelower part of the first zone of the condenser in which the metal vaporscondense to the liquid state, and means to maintain the upper part ofsaid chamber provided with said oriice through which the metal isdischarged to the ingot mould at the same temperature as the ilrst zoneof the condenser, the lower part of said chamber being maintained at asuitable temperature to have the metal deposited in the ingot mould inthe solid state.

6. Apparatus for the production of a metal by condensation of its vaporswhich comprises a reaction chamber for the heat treatment of the oreunder vacuum, a condenser comprising two successive zones communicating'one with the other, the iirst zone communicating with the reactionchamber andthe second zone with a vacuum pump, means to establish andmaintain in said zones respectively temperature and pressure conditionsadapted to cause the metal vapors to condense in the first zone to theliquid state and in the second zone to the solid state, thecommunication between the two zones'being arranged to create in thevapors current sucked by the vacuum pump a loss of pressure capable ofensuring the required difference of pressure between the rst zone andthe second zone, a tight chamber in which is placed an ingot mould toreceive the metal, said chamber communicating by an orice through itsupper part with the lower part of the rst zone of the condenser in whichthe metal vapors condense to the liquid state, and means to maintain theupper part of said chamber provided with said orifice through which themetal is discharged to the ingot mould at the same temperature as thefirst zone of the condenser, the other part of said chamber being heatinsulated during the discharge of the liquid metal tothe ingot mould andthe filling of said mould with the liquid metal.

7. Apparatus for the production of a metal by condensation of its vaporswhich comprises a reaction chamber for the heat treatment of the oreunder vacuum, a condenser comprising two successive zones communicatingone with the other. the first zone communicating with the reactionchamber and the second zone with a vacuum pump, means to establish andmaintain in said zones respectively temperature and pressure conditionsadapted to cause the metal vapors to condense in the rst zone to theliquid state and in the second zone to the solid state, thecommunication between the two zones being arranged to create in thevapors current sucked by the vacuum pump a loss of pressure capable ofensuring the required difference of plessure between the first zone andthe second zone, a tight chamber in which is placed an ingot mould toreceive the metal, said chamber communicating by an orice through itsupper part with the lower part of the first zone of the condenser inwhich the metal vapors condense to the liquid state, and means tomaintain said chamber at the same temperature as the rst zone of thecondenser during the discharge of the liquid metal to the ingot mouldand the filling of said mould with the liquid metal.

8. Apparatus for the production of a metal by condensation of its vaporswhich comprises a reaction chamber for the heat treatment of the oreunder vacuum, a condenser comprising two suci cessive zonescommunicating one with the other, the first zone communicating with thereaction chamber and the second zone with a vacuum pump, means toestablish and maintain in said zones respectively temperature andpressure conditions adapted to cause the metal vapors to condense in therst zone to the liquid state and in the second Zone to the solid state,the communication between the two zones being arranged to create in thevapors current sucked by the vacuum pump a loss of pressure capable ofensuring the required difference of pressure between the first zone andthe second zone, a tight chamber in which is placed an ingot mould toreceive the metal, said chamber communicating by an orifice through itsupper part with the lower part of the first zone of the condenser inwhich the metal vapors condense 4to the liquid state, means to maintainthe upper part of said chamber provided with saidorifice through which 8the metal is discharged to the ingot mould at the same temperature asthe first zone of the condenser, and other means for heating the otherpart of said chamber during the discharge of the liquid metal to theingot mould and the filling of said mould with the liquid metal.

9. Apparatus for the production of a metal by condensation of its vaporswhich comprises a reaction chamber for the heat treatment of the oreunder vacuum, a condenser comprising two successive zones communicatingone with the other, the iirst zone communicating with the reactionchamber and the second zone with a vacuum pump, means to establish andmaintain in said zones respectively temperature and pressure conditionsadapted to cause the metal vapors to condense in the first zone to theliquid state and in the second zone to the solid state, thecommunication between the two zones being arranged to create in thevapors current sucked by the vacuum pump a loss of pressure capable ofensuring the required difference of pressure between the first zone andthe second zone, a tight chamber in which is placed an ingot mould toreceive the metal, said chamber communicating by an orifice through itsupper part with the lower part of the rst zone of the condenser in whichthe metal vapors condense to the liquid state, means to maintain theupper part of said chamber provided with said orifice through which themetal is discharged to the ingot mould at the same temperature as thefirst zone of the condenser, the other part of said chamber being heatinsulated during the discharge of the liquid metal to the ingot mouldand the filling of said mould with the liquid metal, and cooling meansadapted to be substituted for the heat insulating means of the ingotmould chamber after the filling of the ingot mould and before it istaken out of the chamber.

l0. Apparatus for the production of a metal by condensation of itsvapors which comprises a reaction chamber for the heat treatment of theore under vacuum, a condenser comprising two successive zonescommunicating one with the other, the rst zone communicating with thereaction chamber and the second zone with a vacuum pump, means toestablish and maintain in said zones respectively temperature andpressure conditions adapted to cause the metal vapors to condense in thefirst zone to the liquid state and in the second zone to the solidstate, the communication between the two zones being arranged to createin the vapors current sucked by the vacuum pump a loss of pressurecapable of ensuring the required difference of pressure between the rstzone and the second zone, a tight chamber in which is placed an ingotmould to receive the metal, said chamber communieating by an orificethrough its upper part with the lower part of the first zone of thecondenser in which the metal vapors condense to the liquid state, meansto maintain the upper part of said chamber provided with said oricethrough which the metal is discharged to the ingot mould at the sametemperature as the iirst zone of the condenser, other means for heatingthe other part of said chamber during the discharge of the liquid metalto the ingot mould and the filling of said mould with the liquid metal,and cooling means adapted to be substituted for the heating means of theingot mould chamber after the filling of the ingot mould and before itis taken out of the chamber.

11. Condensing apparatus for the production 9 o! magnesium or the likecomprising a plurality of airtight chambers, means to deliver metalvapors to one of the chambers, means to evacuate the other of thechambers, means connecting the chambers of such size that' asubstantially constant diilerence in pressure exists within them whenthe evacuating means is in operation, and means to maintain the chambersat selected temperatures whereby part o1' the vapors may be condensed inone and part in the other chamber.

12. Condensing apparatus for the vapors of magnesium. or the likecomprising a chamber maintained under conditions of temperature andpressure adapted to condense the vapors of a metal to a liquid, andmeans to receive the condensate comprising an ingot mold containing andf surrounded by oil.

l0 other of said chambers at a temperature and a pressure adapted tocondense, the vapors ofthe metal to a solid, and means to remove thesolidcontaining chamber.

\ GEORGES BASSEREAU.

REFERENCES CITED The following' references are of recrd'in the le oi`this patent:

UNITED STATES PATENTSr Number Name Date 1,884,993 Hansgirg Oct. 25, 19322,219,059 Suchy et al. Oct. 22, 1940 2,238,908 McConica Apr. 22, 19412,251,906 Hanawalt Aug. 12. 1941 2,268,779 Seifert Jan. 6; 19422,312,811 Gentil Mar. 2, 1943 2,362,440 A Hertel Nov. 14, 1944 2,381,405Griswold Aug. 7, 1945 FOREIGN PATENTS Number I Country Date 503,245Great Britain Apr. 4, 1939

11. CONDENSING APPARATUS FOR THE PRODUCTION OF MAGNESIUM OR THE LIKECOMPRISING A PLURALITY OF AIRTIGHT CHAMBERS, MEANS TO DELIVER METALVAPORS TO ONE OF THE CHAMBERS, MEANS TO EVACUATE THE OTHER OF THECHAMBERS, MEANS CONNECTING THE CHAMBERS OF SUCH SIZE THAT ASUBSTANTIALLY CONSTANT DIFFERENCE IN PRESSURE EXISTS WITHIN THEM WHENTHE EVACUATING MEANS IN ONE OPERATION, AND MEANS TO MAINTAIN THECHAMBERS AT ASELECTED TEMPERATURES WHEREBY PART OF THE VAPORS MAY BECONDENSED IN ONE AND PART IN THE OTHER CHAMBER.